Problem With Sea Lions On Swim Platform

[JayG]

Hello everybody. I keep my Meridian 441 at our yacht club in Marina Del Rey.
I have an on going problems with seals who love to rest their dirty bodies on my swim step and leaving quite a mess. I have put buckets filled with water to block the seals but they still manage to jump aboard. They are rather belligerent and only leave when I squirt a hose on them.
I would prefer not to drill holes in my swim platform to install barriers that would keep them off the platform.
Wondering what other methods people have used to solve this problem?
Thanks for any help you may offer.